Can somebody read this passage help me with the answer

Look at the answer options, then look through the passage.

Explanation:

Which of the ideas from the answer options has been repeated throughout the passage? That would be your main idea.

B

Explanation:

Through my reading of the passage, there really isn't an emphasis on a specific sleeping disorder as each was mentioned and explained.  Thus, option B becomes suitable as it relates to the many different types and variety of sleeping disorders.